daf bit: Zevachim 68

Animals brought as offerings need to be fit for the purpose, for example unblemished. An animal that is not fit not only isn't a valid offering but can cause ritual impurity in those who handled it. What happens if something causes it to become unfit after it's been dedicated? The mishna is currently talking specifically about birds, and says: if an unfit person performed the ritual, or if the priest used the wrong hand or did it at night, or if he did it in the wrong place within the sanctuary, it does not cause this ritual impurity. However, if he used a knife (for birds they pinch off the head), or if he offered turtle-doves when they're too young or pigeons when they're too old, or if he offered a bird with a crippled wing or a missing foot, all these cause ritual impurity. The general rule is: all those whose unfitness arose within the sanctuary do not defile, but those that were already unfit do. (68a-b)

Using a knife sounds like something that arose within the sanctuary. I don't see anything here that addresses this, but I should note again that this tractate is very technical and dense and I'm sure I'm missing stuff.

Today's daf is 69.